1. Field of the Invention
The present invention relates to a mechanism for operating a ramp member in an access opening in a vehicle. It is particularly designed for deploying and stowing a wheelchair ramp at the entranceway of a bus by rotation around an axis close to the side of the bus.
2. Prior Art
Various ramp operating systems for buses and other vehicles are known in the art. Some have a complex link arrangement allowing them to lift a chair while remaining horizontal. Some slide out from underneath the floor of the bus and tilt down. Others are stowed in a vertical position and are pivoted about a horizontal hinge. The present invention is concerned with a "flip-out" type of ramp which is normally stowed in a horizontal position in a recess in the bus floor, and is pivoted upward and outwards to a downward sloping extended position, after the bus door has been opened. Such a ramp needs an operating mechanism by which it can be rotated through more than 180.degree..
Prior art operating systems for use with such flip-out ramps use a gear drive or hydraulic cylinder mechanism to pivot the ramp outward. However, with such prior art systems, the ramp cannot be moved manually in the event of a failure of the power source unless the drive mechanism is first disengaged. The need to disengage the drive mechanism in the event of a failure of the power source and to re-engage the mechanism afterwards, is a serious disadvantage to such systems. Further, such prior art hydraulic cylinder drive mechanisms do not give the range of movement to permit the ramp to be pivoted under hydraulic control through more than 180.degree.. In addition, such prior art systems require complex safety arrangements to prevent the ramp from moving with such force as to crush obstacles that get in the downward path of the ramp.